(a) Field of the Invention
The present invention relates to a data transmission system and method in an EPON, and a recording medium storing a program of the same. More particularly, the present invention relates to a data transmission system and method in an EPON, and a recording medium storing a program of the same that realizes function architecture of a MAC (medium access control) control sublayer of an ONU (optical network unit) for controlling data transmission to an OLT (optical line transmission) from an ONU or ONT (referenced only as ONU below) in an Ethernet-based PON.
(b) Description of the Related Art
At present, ADSL (asymmetric digital subscriber line) and cable modem systems are most commonly used for high-speed Internet service. The ADSL system uses telephone lines to provide high-speed Internet access. An ADSL modem is installed in a subscriber's computer, and high-speed service between 2 Mbps and 10 Mbps is possible therewith.
A cable modem system uses the coaxial cable of a local cable TV line to realize high-speed Internet service. The subscriber using this system must have a cable TV hook-up and a cable modem installed in his or her PC.
High-speed Internet services provide far faster data transmission rates of 2 Mbps—10 Mbps than a conventional system using a telephone line modem, which provides Internet access speeds of 56 Kbps. As a result, high-speed Internet services provide greater user satisfaction when surfing the Web (HTTP), sending E-mail, transmitting files (FTP), etc. However, the needs of the user are not so fully addressed when using high-speed Internet services such as VoIP (voice over Internet protocol), VoD (video on demand), Internet broadcasting, etc.
Further, with increases in the number of subscribers using the cable modem system, the bandwidth that can be used is decreasing. The problem of decreasing available bandwidth is also a problem when using the ADSL method for high-speed Internet access as a result of the increasing distances between the telephone company office and the subscriber's location.
To address these problems, FTTH (fiber to the home), FTTB (fiber to the building), and FTTC (fiber to the curb) systems are provided in which optical cables are installed that lead to homes, offices, etc. To reduce the price of such systems, much research is being performed with respect to the E-PON (Ethernet-passive optical network).
In order to make the system more price competitive, the E-PON is a network that does not utilize an active element that uses power in an optical subscriber network, and instead uses a passive element, and combines Ethernet technology.
Standards for E-PON are set forth in the IEEE (Institute of Electrical and Electronics Engineers) 802.3ah Ethernet in the First Mile Task Force.
In an E-PON, a point-to-multi-point structure is used to connect a plurality of ONUs to one OLT port through a splitter, which is a passive element.
Data is transmitted between the OLT and the ONUs through Ethernet frames, with a downstream signal from the OLT to the ONUs transmitting data through broadcasting, and an upstream signal from the ONUs to the OLT using a time division multiple access (TDMA) method so that the ONUs divide the bandwidth allocated to themselves.
FIG. 1 is a schematic view of a conventional MAC control sublayer.
As shown in FIG. 1, a conventional MAC control sublayer 20 includes a parser 21 for classifying frames transmitted from a MAC client 10, a PAUSE block 22 for generating and ending PAUSE frames, a multiplexer 23, and a demultiplexer.
The PAUSE block 22 temporarily discontinues data transmission the multiplexer 23 performs multiplexing of paused frames and frames received from the MAC client 10, and the demultiplexer classifies the paused frames.
In the MAC control sublayer 20 structured in this manner, multiplexing and transmission are performed of only frames transmitted from a bridge, which allows transmission of frames that must be relayed after distinction of MAC addresses of terminals for transmission with an external network, and of PAUSE frames.
Accordingly, since the conventional MAC control sublayer does not multiplex other control frames transmitted from the bridge for upstream frame transmission or frames transmitted from a processor, and does not support DBA (dynamic bandwidth allocation), the transmission order and time of frames from the bridge are unable to be directly controlled.